[Build, IGS] Ignore non-existing keys during setup file parsing

#KTI-1223 In Progress

repo/gradle-settings-conventions/internal-gradle-setup/src/main/kotlin/SetupFile.kt

@@ -18,6 +18,10 @@ internal data class SetupFile(
     val properties: Map<String, String>,
 )
 
+private val json = Json { ignoreUnknownKeys = true }
+
 // can't use decodeFromStream: https://github.com/Kotlin/kotlinx.serialization/issues/2218
 internal fun parseSetupFile(inputStream: InputStream): SetupFile =
-    Json.decodeFromString(BufferedReader(InputStreamReader(inputStream)).lines().asSequence().joinToString("\n"))
+    json.decodeFromString(
+        BufferedReader(InputStreamReader(inputStream)).lines().asSequence().joinToString("\n")
+    )

repo/gradle-settings-conventions/internal-gradle-setup/src/test/kotlin/SetupFileParseTest.kt

@@ -8,15 +8,11 @@ package org.jetbrains.kotlin.build
 import kotlin.test.*
 
 class SetupFileParseTest {
-    private fun openPropertiesJsonStream() =
-        SetupFileParseTest::class.java.classLoader.getResourceAsStream("properties.json")
+    private fun openPropertiesJsonStream(name: String) =
+        SetupFileParseTest::class.java.classLoader.getResourceAsStream("$name.json")
             ?: error("No properties.json file found in test resources")
 
-    @Test
-    fun testSimpleParsing() {
-        val setupFile = openPropertiesJsonStream().use {
-            parseSetupFile(it)
-        }
+    private fun assertSampleSetupFileIsParsedCorrectly(setupFile: SetupFile) {
         assertEquals(
             mapOf(
                 "newProperty1" to "someValue",
@@ -26,4 +22,20 @@ class SetupFileParseTest {
             setupFile.properties
         )
     }
+
+    @Test
+    fun testSimpleParsing() {
+        val setupFile = openPropertiesJsonStream("properties").use {
+            parseSetupFile(it)
+        }
+        assertSampleSetupFileIsParsedCorrectly(setupFile)
+    }
+
+    @Test
+    fun testUnknownFieldsDoNotBreakParsing() {
+        val setupFile = openPropertiesJsonStream("properties-with-unknown-fields").use {
+            parseSetupFile(it)
+        }
+        assertSampleSetupFileIsParsedCorrectly(setupFile)
+    }
 }

repo/gradle-settings-conventions/internal-gradle-setup/src/test/resources/properties-with-unknown-fields.json

@@ -0,0 +1,8 @@
+{
+  "properties": {
+    "newProperty1": "someValue",
+    "newProperty2": "someOtherValue",
+    "alreadySetProperty": "newValue"
+  },
+  "unknownField": "someValue"
+}